The present invention relates to an apparatus for making a tubular length of stretch film.
More specifically, the tubular length of film is used to wrap packages containing groups of products such as bottles with bases of different shapes—for example, circular, square or rectangular—or even containers made of metal (including parallelepiped shaped containers).
At present, in the packaging of groups of plastic bottles (to which the present description will hereinafter refer, although the invention may also be applied to other types of product or container), the final wrapping over the groups of bottles usually consists of a sheet of heat-shrink or stretch film.
In some cases and for some types of products, packaging lines that use heat-shrink film may, however, be very expensive for the manufacturer for a number of reasons: each line must have several different operating units, such as product collating units (especially in the case of continuous lines), and film feed and heating units. Moreover, all these units require a large number of control devices and accessory parts.
Other negative factors to be taken into account when dealing with packaging lines of this kind are the high cost of the heat shrink film itself and the fact that some products cannot be heated beyond certain limits, which means that heat shrink wrapping solutions are not feasible.
Wrapping machinery and methods that use stretch film, on the other hand, are more economical to run and have a simpler structure, while providing end products of the same quality as heat shrink wrapping lines.
In this connection, and in view also of the greatly increased demand for stretch wrapping, there has also been a growing demand for a new type of end package to meet changing consumer requirements and to facilitate handling.
One prior art solution that uses stretch film is described in European patent application No. 01830521.9 by the same Applicant as the present, where the stretch wrapping machine essentially comprises:
a feed table on which the groups of products presenting a front face and a longitudinal dimension are formed;
a first station for making the packages, located on and forming part of the feed table, and being equipped with first means for unwinding the stretch film and forming a length of the stretch film wound around first means for preforming the package located on the feed table and mobile between several working positions where the tubular length of film is stretched open wide, the group of products fed into it, and the wrapped package fed back out onto the feed line once the stretch film has shrunk back to its original size.
From this basic concept for a packaging line, to which at least one other station may be added to apply a second length of stretch film to the package that has already been wrapped once and turned through ninety degrees, the Applicant proceeded to the stage of actually constructing the operating stations forming part of the packaging line, including the station forming the subject matter of this invention and embodying the above mentioned first means for unwinding the stretch film to form the length of stretch film.
The present invention therefore has for an aim to provide an apparatus for making a tubular length of stretch film applicable to machines of the above mentioned type and having characteristics of high precision, adaptability to products of different shapes and sizes, and constructional simplicity, combined with speed of unwinding and positioning the film.